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ORIGINAL: RugerM77.270
I'm looking at getting a .308 and start to shoot at extended range out to about 600 yards. I've noticed that some people want to use a short barrel say 20 or 22 inches them some are 26 inches. I would think that the longer barrel would be better but if it is how much better and why? I know you gain 15-20 feet for every inch but what does that add up to in ballistics?
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You gain 15-20 feet per second up to a point.
Every cartridge has its magic barrel length. I have no idea what it is for a .308, but I suspect its somewhere in the 20-22" region. A .22 LR for example, has a magic barrel length of 16". What does this mean? At that point, all your powder is burned and your bullet is going as fast as it will go. Much anything past that point is just extra and could even theoretically slow you down.
There are more variables with a .308, especially if you are a handloader, because you can load faster or slower burning powder. So the magic barrel length number will change a bit. To be honest, I think there are many more important considerations that lead up to accuracy than barrel length..... most of them have to do with having a squared action that is properly beaded and a properly headspaced bolt and chamber.
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My plan is to get a Remington SPS Tactical 20'' barrel or Varmint 26'' barrel to learn the basics and also buy some reloading equipment before I move into the big custom rifles.
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That makes if fairly easy. All you have to fool with is reloading, which is fun, education and addictive.
Here are my thoughts on barrel length... just for what its worth...
When you fire a rifle, your barrel oscilates, just like the amplitude on radio waves, or a limber 10 foot length of 1/2" PVC pipe. The key to being accurate is having your bullet leave on exactly the same amp frequency or wave each time. Hopefully this is making sense to you. As your barrel heats up, its oscillation is more extreme, the waves/whipping gets larger... thats why hot barrels frequently throw shots high or low, but not side to side.
Now, take my PVC example.... say you have a 1/2" PVC pipe 10' long. You can hold it in the middle and shake it, and it will flex and bend like a 4 weight fly rod. In turn, take a 6" section of it, and would take a hydrolic press to flex it. In my opinion/experience, the same principal applies to rifle barrels. The shorter the barrel, the less the flex, the easier it is to have the bullet leave on the same wave/whip every time. There is a law of deminishing returns, however, because your ability to shoot the gun well with a short sight radius drops drastically (it is much less forgiving, which is why its hard to be accurate at longer ranges with even longer barreled handguns as opposed to rifles, as tiny form flaws are exponentially magnified downrange). This is also why bull/heavy barrels tend to shoot more accurately than their tapered counterparts, because they are stiffer and flex less while firing.
Also, as you pointed out, you start losing velocity, and if all your powder isn't being burned up, you could not be getting the exact same amount of pressure/velocity each time. Moreover, of course, a shoulder fired "rifle" cannot by federal law have less than a 16" barrel... so there is that consideration too.
This makes sense to me. Could it be totally way the heck off... sure I guess so, but thats how it was explained to me when I was a bit younger, and its been my experience that it holds true for the most part. Most of the really knockout rifles I have, use barrels under 24" in length. This is also part of the reason (I believe) that a lot of folks are not pleased with the accuracy out of their TC Pro Hunters.... because they all come with those long 28" barrels that really aren't all that heavy.
Sorry to ramble on... hope I was able to shed some light.
How important is barrel length?
